This project deals with applications of C13 Fourier transform NMR to studies of biological systems. Single-carbon resonances of proteins in solution will be used as probes of molecular conformation. C13 resonances of minor bases of tRNA will be used for studying the role of minor bases in the structure of tRNA. The mobilities of the various types of lipids within the several classes of human plasma lipoproteins will be determined through measurement of the appropriate spin-lattice relaxation times. These measurements will be extended to a variety of modified preparations derived either by differential extraction of various lipids or by specific hydrolysis of both lipids and proteins by the corresponding hydrolytic enzymes. The dependence of the spin- lattice relaxation times on the presence or structural integrity of certain specific components will permit us to generate more sophisticated structural models for these complex substances. Efforts will be made to study the dynamic behavior of intact biological membranes by means of C13 Fourier transform nmr.